The fountain of the luminous infrared galaxy Zw049.057 as traced by its OH megamaser

¹ Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, 439 92 Onsala, Sweden
² Leiden Observatory, Leiden University, Post Office Box 9513 2300 RA Leiden, The Netherlands
³ Instituto de Astrofísica de Andalucía, Glorieta de la Astronomía, s/n, 18008 Granada, Spain
⁴ Jodrell Bank Centre for Astrophysics, Department of Physics and Astronomy, The University of Manchester, Manchester M13 9PL, UK
⁵ National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA
⁶ Wisconsin IceCube Particle Astrophysics Center, Madison, WI 53703, USA
⁷ Department of Physics and Astronomy, Macalester College, 1600 Grand Ave, St. Paul, MN 55105, USA
⁸ Observatoire de Paris, LERMA, Collège de France, CNRS, PSL University, Sorbonne University, Paris, France
⁹ Astrophysics, Department of Physics, University of Oxford, Keble Road, Oxford OX1 3RH, UK
¹⁰ School of Sciences, European University Cyprus, Diogenes Street, Engomi, 1516 Nicosia, Cyprus
¹¹ Universidad de Alcalá, Departamento de Física y Matemáticas, Campus Universitario, 28871 Alcalá de Henares, Madrid, Spain
¹² Max-Planck-Institut für Radioastronomie Auf dem Hügel 69, 53121 Bonn, Germany
¹³ Department of Astronomy, The University of Tokyo, 7-3-1, Hongo, Bunkyo, Tokyo 113-0033, Japan
¹⁴ Instituto de Estudios Astrofísicos, Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Av. Ejército Libertador 441, Santiago, Chile
¹⁵ Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, China

Received: 22 March 2024
Accepted: 4 June 2024

Abstract

High-resolution ($0\stackrel{″}{.}037-0\stackrel{″}{.}13$ [10 − 35 pc]) e-MERLIN (λ6 − 18 cm) and ($0\stackrel{″}{.}024$ [6.5 pc]) ALMA (λ1.1 mm) observations have been used to image OH (hydroxyl) and H₂CO (formaldehyde) megamaser emission, and HCN 3 → 2 emission toward the nuclear (< 100 pc) region of the luminous infrared galaxy Zw049.057. Zw049.057 hosts a compact obscured nucleus (CON), and thus represents a class of galaxies that are often associated with inflow and outflow motions. Formaldehyde megamaser emission has been detected toward the nuclear region, ≲30 pc ($0\stackrel{″}{.}1$), and traces a structure along the disk major axis. OH megamaser (OHM) emission has been detected along the minor axis of the disk, ∼30 pc ($0\stackrel{″}{.}1$) from the nucleus, where it exhibits a velocity gradient with extrema of −20 km s⁻¹ southeast (SE) of the disk and −110 km s⁻¹ northwest (NW) of the disk. HCN 3 → 2 emission reveals extended emission, along the disk minor axis out to ∼60 pc ($0\stackrel{″}{.}2$). Analysis of the minor axis HCN emission reveals high-velocity features extending out to 600 km s⁻¹, redshifted on the SE side and blueshifted on the NW side. We propose that the high-velocity HCN emission traces a fast (> 250 km s⁻¹) and collimated outflow that is enveloped by a wide-angle and slow (∼50 km s⁻¹) outflow that is traced by the OHM emission. Analysis of the outflow kinematics suggests that the slow wide-angle outflow will not reach escape velocity and will instead fall back to the galaxy disk, evolving as a so-called fountain flow, while the fast collimated outflow traced by HCN emission will likely escape the nuclear region. We suggest that the absence of OHM emission in the nuclear region is due to high densities there. Even though OHMs associated with outflows are an exception to conventional OHM emission, we expect them to be common in CON sources that host both OHM and H₂CO megamasers.